The Universal Mobile Telecommunications System (UMTS), also known as the third generation of wireless communications systems, is currently being added to the 1st and 2nd generation of wireless communications systems (such as for instance GSM850, GSM900, DCS, PCS1900, CDMA, or TDMA) and has stimulated the demand for multiband antenna arrays and, in particular, for triple-band base station antenna arrays. Such triple-band antenna arrays integrate the 1st, 2nd, and 3rd generation of wireless communications systems.
A typical cellular service requires a network of base stations, each of them comprising several base station antenna arrays, to provide coverage to the users of said cellular service. The antenna arrays are the radiating part of the base station. Usually, the radiating part of the base station is composed by nine or three independent antenna arrays that give service to, for example, a specific part of a city, a village, a road, or a motorway. Since the radiating part of the base station is composed by several antenna arrays, the dimensions of a conventional base station are large and the resulting base station has a significantly big visual impact.
One possibility to enable a base station to provide coverage for three different mobile communication systems is to use for example three single-band antenna arrays (for example one for GSM900, another for DCS and a third one for UMTS). Since typical base stations split their area of coverage into three different sectors, three single band antenna arrays are required for each of said sectors, which means that the triple-band three-sector base station might require up to a total of nine antenna arrays. As an alternative, and in order to reduce the antenna array count for the base station, two out of the three operation bands could be combined in a dual-band antenna array (such as for instance DCS and UMTS). In this case only two antenna arrays would be necessary in each sector, resulting in a total of six antenna arrays for a triple-band three-sector base station. The use of multiple single-band antenna arrays (or a combination of single-band and dual-band antenna arrays) in a triple-band base station will typically lead to bulky and mechanically complex structures, hardly disguisable with the surrounding environment. Furthermore, a large antenna array count will likely result in a costly solution.
As an alternative, some conventional triple-band antenna arrays that are used today for base stations make use of a side-by-side configuration, in which three single-band antenna arrays are arranged one next to another along the direction defined by the width of the single-band antenna arrays and packed in a single dielectric enclosure or radome.
Although, this approach reduces the number of antenna arrays in the base station to just three (i.e., one per sector), it still performs poorly in terms of minimizing the visual impact of the base station, as the dimensions of these antenna arrays, specially their width, are significantly larger than the dimensions of a single-band antenna array.
Nowadays, local, regional and/or national governments and public administrations are concerned about the visual impact of the base stations in their cities, mainly because of the large size of the antenna arrays. As governments and public administrations endeavor in minimizing the visual impact of the base station of cellular communications networks, it is becoming more and more difficult for network operators and mobile service providers to acquire new sites and/or obtain the license to set up new base stations in cities and villages around the world.
The visual impact due to the size and number of antenna arrays in a base station has been a rising issue for network operators and consumers, creating the demand for smaller-sized antenna arrays for base stations, with which to reduce substantially the visual impact of the base station but without compromising the level of performance and functionality of current solutions.
Adjustable electrical down-tilt techniques for antenna array systems are very well known in the related background art.